Parts these are Cd be Icfc, 88 allo how frequent
and large, will be Jhewn more dillinclly when
wc come to treat os the Ornaments of Edifices;
We sinali only observe here, that they not only
add ro the beauty of the Work, but alio sive 0
sonie Ex pence, as they make less Stone and I.ime
to serve sor the Walling. This chiessy is to be
taken care of, that you makethese Niches incon-
venient Numbers, not too big and of a jutt form ;
and lo as in their order to imitate the Windows,
And let them be as you will, 1 have remark'd
in the Structures of the Ancients, that they ne-
ver used to suller them to take up above the
seventh Part of the Front, nor less than the
ninth. The Spaces between the Columns are to
be reckoned among the principal Apertures, and
are to be left variousiy according ro the variety
os Buildings. But we ih;:!] J peak of these more
clearly in their proper Place, and chielly when
we treat of Sacred Edisices. Let it be sussicient t
to premile here, that thole Openings ihou'd be
left in sucha manner, as to have particular Res-
peft to the Nature of the Columns, which are
design'd for the Support of the Covering; and
firll, that those Columns be not too smaJl, nor
Hand too thin, so as not to be duly able to
bear the Weight, nor too big, or set io thick as
not to leave open convenient spaces for Passage.
I.allly, the Apertures mud be difserent, when the
Columns are frequent from what they are when
they {land thin, because over frequent Columns
we lay an Architrave, and over the others we turn
an Arch. But in all Openings over which wc
make Arches, we ihou'd contrive to have the Arch
never lets than a half Circle, with an Addition
of the seventh Part of half its Diameter : the molt
experienced Workmen having found that Arch
to be by much the bed adapted for enduring in a
manner ro perpetuity ; all other Arches be-
ing thought less ilrong for supporring the Weight,
and more liable .to ruin. It is moreover imagi-
ned, that the half Circle is the only Arch which
has no occasion either for Chain or any other
Fortification ; and all others is you don t either
chain them or place some Weight again'l them for
a Counterpoise, are found by their own Weight
to buril out and fall to ruin. I will not omit
here what I have taken notice of among the An-
cients, a contrivance certainlv vcrv excellent and
praiie-worthy : their bell Architects placed thest
Apertures and the Arches of the Pools or their
Temples in inch a manner, that even tho' you
took away every Column srom under them, yet
they wou'd Hill Hand sirm and not sill down, the
K Aahcs